The present invention relates to a process and apparatus for edging and polishing of an ophthalmic lens and, more specifically, a process and apparatus for edging and polishing a surface of an ophthalmic lens comprising polycarbonate, CR 39 or glass, wherein the step of edging and polishing may be performed with a single machine and the step of polishing may be performed with a single polishing wheel.
In an alternate embodiment, a process for simplified shaping and polishing of an optical surface of a lens is provided.
In the lens grinding industry a great number of ophthalmic labs have sprung up with the advent of modern bevel edger machines. These machines are capable of taking a lens blank and grinding a final shape of a lens for fitting of the lens in a particular frame. Thus, a lens blank of the proper prescription is rough cut to the rough shape of the frame and thereafter a bevel edge is ground on the lens such that the lens will properly fit in the glasses frame. Such procedures are known in the art and explained in the owner's manual of AIT and WECO bevel edger machines which are incorporated herein by reference. A final step of polishing the bevel edge is also employed to provide a lens edge with a high luster finish.
Typically, the steps of rough-cutting the lens, bevel edging and polishing are performed with different machines as required for various lens materials, i.e., polycarbonate, CR 39 or glass. The step of finishing also utilizes different grinding wheels depending on the lens material. This typically requires the lens grinding labs either to have separate machines with various grinding wheels or to send out work which cannot be done on a single existing machine commonly found in ophthalmic labs of today. The requirement of different machines is in part due to lenses made of polycarbonate require special wheels for grinding and typically utilize no coolant; whereas CR 39 plastic lenses require different wheel coolant or a lubricant (generally water) when grinding. This is because of the thermoplastic nature of the polycarbonate, which will flare in its thickness at the grinding edge if coolant or a lubricant is utilized during removal of material. Polycarbonates are therefore usually dry ground and thereafter polished at their edges on a separate machine. A further problem of combining the polycarbonate and CR 39 edging and polishing process is that a finishing wheel that is fine enough to polish CR 39 is too fine to grind polycarbonate lenses. The hardness of polycarbonate materials is also problematic because it causes excessive wear of polishing wheels commonly used for polishing of other materials.
Typically, the finishing and polishing steps are accomplished via two separate abrasive wheels with the "roughing" of the lens accomplished via a separate machine or a separate abrasive wheel in the same machine. In recent years, the market for ophthalmic lenses has become increasingly interested in achieving a polish on the edge of the lens which is equal in finish to the optical surfaces of the lens. In the past, this was accomplished by time consuming polishing with hand tools or the like. While there are a few mechanical polishing systems, they typically do not provide hand polished results and are exclusively used for a single type of lens material.
Additionally, shaping and polishing of a lens is very time consuming particularly in the lens lapping phase of the invention. This process requires lapping with several different grades of abrasives to reach the final optical and polished surface.
Thus, there remains a need in the art to provide a system for providing an optical quality polish on all common lens blank materials including polycarbonate, CR 39 plastic and glass on a single machine and polishing all common types of lens blank materials with a single polishing wheel system.